ROTATION SYSTEM THAT CAN BE USED WITH A CONTROL DRUM IN A NUCLEAR ENVIRONMENT

Abstract

A rotating apparatus can be used with a control drum in a nuclear environment. The control drum is mounted on a shaft that can rotate around a horizontal axis, and the control drum includes an absorbent portion and a reflective portion. The rotating apparatus includes a rotation mechanism designed to apply a force to the shaft in an operating position, pushing it to rotate to a stopped position. This force is resisted by a motor to hold the shaft in the operating position when the motor is energized. The force is not resisted when the motor is de-energized. The rotating apparatus also includes a rotation management system that controls the shaft's rotation.

Description

ROTATING APPARATUS FOR USE WITH A CONTROL DRUM IN A NUCLEAR ENVIRONMENT AND CONTROL DRUM APPARATUS COMPRISING IT BACKGROUND 1. Field The concept revealed and claimed refers, in general, to nuclear power generation equipment and, more specifically, to a rotating apparatus that can be used in conjunction with a control drum employed in a nuclear environment. 2. Related Technique Numerous types of nuclear fission reactors are known in the relevant art. In general, such nuclear reactors include a reactor vessel containing a quantity of fissile material and several control structures that regulate the reactivity of the nuclear fission reaction. In certain types of nuclear reactors, control rods are used as these control structures. These control rods are inserted at varying distances into the fissile material, where they act as absorption devices that progressively reduce the reactivity of the fission reaction as they penetrate the material. Another type of control structure is a control drum, which is roughly cylindrical in shape and mounted on a pivoting shaft. The control drum includes a reflective portion and an absorbing portion. The shaft can rotate around an axis of rotation to cause the reflective portion to... 1679196 of 22 The reflector is oriented toward a core of the nuclear environment in an operating state of the nuclear environment. The shaft is rotated around the axis of rotation to cause the absorbing portion to be oriented toward the core, resulting in a reactor shutdown condition. For example, the reflector portion reflects neutrons back to the core in the operating state, and the reflector portion absorbs neutrons in the shutdown state. While control drums of this type have generally been effective for their intended purposes, they have not been without limitations. These control drums are typically rotated by stepper motors that require electrical power to operate. In a situation requiring an emergency reactor shutdown, a lack of electrical power to operate the stepper motors and move the control drums to the shutdown positions could potentially result in a catastrophic situation. Furthermore, if the nuclear environment is physically transportable from one location to another, it is desirable to ensure that the absorbing portion of the control drum is oriented toward the core to prevent a possible unintentional reactor startup. Such an unintentional reactor startup could potentially occur if the reflecting portion of the control drum is inadvertently repositioned to face, either partially or completely, toward the core.While the stepper motors that typically control the control drums can maintain an orientation of the control drum such that the reflective portion is away from the core, such control can potentially be lost if any of such a stepper motor loses electrical power, and transporting the nuclear environment from one location to another poses a significant challenge. 1679196 of 22 potential for electrical power loss. Therefore, improvements would be desirable. SUMMARY An improved rotating apparatus can be used with a control drum in a nuclear environment. The control drum is mounted on a shaft that can rotate around a horizontal axis, and the control drum includes an absorbing portion and a reflecting portion. The rotating apparatus includes a rotation mechanism designed to apply a force to the shaft in its operating position, pushing it to rotate to a stopped position. This force is resisted by a motor to hold the shaft in the operating position when the motor is energized. The force is not resisted when the motor is de-energized. The rotating apparatus also includes a rotation management system that controls the shaft's rotation. Accordingly, one aspect of the unveiled and claimed concept is to provide a rotating apparatus that can be operated in the event of an electrical power failure to move a control drum from an operating position to a stopped position. Another aspect of the concept revealed and claimed is to provide a rotating device in such a way that it quickly moves the control drum to the stop position in the absence of electrical power. Another aspect of the unveiled and claimed concept is to provide a rotating device such that it can also retain the control drum in the stopped position when the nuclear environment is being transported from one 1679196 from 22 places to another and in the absence of electrical power in such a situation. Accordingly, one aspect of the disclosed and claimed concept is to provide an improved rotating apparatus that can be used with a control drum in a nuclear environment. The control drum has a shaft that can rotate about a horizontal axis of rotation, a reflective portion located on the shaft, an absorbing portion located on the shaft, and a motor that, when energized, can be operated to move the shaft between an operating position in which the reflective portion is oriented towards a core of the nuclear environment and a stop position in which the absorbing portion is oriented towards the core.Generally speaking, the rotating apparatus includes a rotating mechanism that is structured to apply a force to the shaft in the operating position, a force that is structured to rotate the shaft to the stopped position. This force is resisted by the motor to retain the shaft in the operating position when the motor is energized, and the force is not resisted when the motor is not energized. It also includes a rotating management system that is structured to resist the rotation of the shaft when the shaft is in the stopped position. Other aspects of the disclosed and claimed concept are provided by an improved rotation management system that can be used with a control drum in a nuclear environment. The control drum has a shaft that can rotate about a horizontal axis of rotation, a reflective portion located on the shaft, an absorbent portion located on the shaft, and a motor that, when energized, can be operated to move the shaft between an operating position in which the reflective portion is oriented toward a core of the nuclear environment and a stopped position where the portion 1679196 of 22 absorber is oriented towards the core. It can generally be stated that the rotation management system includes an actuator, a pin that is located on the actuator, and the actuator can be operated to move the pin between a first location coupled with the shaft in the stopped position and a second location uncoupled from the shaft, the pin in the first position is structured to resist rotation of the shaft. BRIEF DESCRIPTION OF THE DRAWINGS A further understanding of the concept disclosed and claimed may be obtained from the following description when read in conjunction with the accompanying drawings, in which: Fig. 1 is a perspective view of an improved control drum apparatus having an improved rotating apparatus according to a first embodiment of the disclosed and claimed concept, wherein the control drum apparatus is in an operative position; Fig. 2 is a view similar to Fig. 1, except that it depicts the control drum apparatus in a stopped position; Fig. 3 is a view of a portion of the control drum apparatus of Fig. 1; Fig. 4 is a view similar to Fig. 3, except that it depicts the portion of the control drum apparatus in the stopped position; Fig. 5 is a view of another portion of the control drum apparatus of Fig. 1; Fig. 6 is a view similar to Fig. 5, except that it depicts the other portion of the control drum apparatus in the stopped position; 1679196 of 22 Fig. 7 is a perspective view of another improved control drum apparatus having an improved rotating apparatus according to a second embodiment of the disclosed and claimed concept, wherein the control drum apparatus is in an operative position; Fig. 8 is a view of a portion of the other control drum apparatus of Fig. 7; Fig. 9 is a view similar to Fig. 8, except that it depicts the portion of the other control drum apparatus in a stopped position; Fig. 10 is a view of another portion of the other control drum apparatus of Fig. 7; and Fig. 11 is a view similar to Fig. 10, except that it depicts the other portion of the other control drum apparatus in a stopped position. Similar numbers refer to similar parts throughout the descriptive report. DESCRIPTION An improved rotating apparatus 4 according to a first embodiment of the disclosed and claimed concept is represented in Figs. 1 and 2 as a part of an improved control drum apparatus 6. The control drum apparatus 6 is a part of a nuclear environment 8 such as could include, by way of example and without limitation, a nuclear reactor, a nuclear power plant. According to what can be understood from Figs. 1 and 2, it can be said that the control drum apparatus 6 includes, in addition to the rotating apparatus 4, a control drum 10, and a shaft 12 on which the 1679196 of 22 control drum 10. The nuclear environment 8 includes a support 14 on which the shaft 12 is rotatably arranged. The control drum 10 can be said to include a reflecting portion 16 that is configured to reflect neutrons in the nuclear environment 8 and an absorbing portion 18 that is configured to absorb neutrons in the nuclear environment 8. The shaft 12 can be rotated about a rotation axis 20 by means of a stepper motor 24 that is connected between the support 14 and the shaft 12. The stepper motor 24 can be electrically operated to rotate the shaft 12 and the control drum 10 located on it between an operating position, as generally represented in Fig. 1, and a stopped position, as generally represented in Fig. 2. In the operating position of Fig.1, the reflecting portion 16 is usually oriented towards a nucleus 22 of the nuclear environment 8 and therefore enhances the reactivity of the fission reaction in the nucleus 22. In the stop position of Fig. 2, the absorbing portion 18 is usually oriented towards the nucleus 22 and absorbs the neutrons to reduce the reactivity of the fission reaction. The control drum apparatus 6 includes the previously mentioned stepper motor 24 and also includes an encoder 27 that is connected to the stepper motor 24 or the shaft 12 and that outputs a series of pulses that are representative of the rotational movement of the shaft 12 around the rotation axis 20. The pulses are detected by a control system of the control drum apparatus 6 in order to continuously determine the rotational position of the control drum 10 with respect to the core 22 and / or with respect to other structures. In the example embodiment shown, the rotation axis 20 is 1679196 of 22 oriented along the horizontal direction, as indicated in item 26. It is understood that the horizontal direction 26 is perpendicular to the vertical direction, as indicated in item 28. The rotating apparatus 4 can be described as comprising a rotating mechanism 30 and a rotating management system 32. As will be explained in more detail below, the rotating mechanism 30 applies a force to the shaft 12 in the operating position to push the shaft to the stopped position. This force is resisted by the stepper motor 24 when it is energized. When the stepper motor 24 is no longer energized, such as in the case of a power failure to the stepper motor 24, the force applied by the rotating mechanism 30 to the shaft 12 is resisted by the stepper motor 24, thus rotating the shaft 12 from the operating position shown in Fig. 1 to the stopped position shown in Fig. 2.Although the word “force” has been used in this document, it is understood that such force is applied to the rotatable shaft 12 and, therefore, it is understood that the word force can be used interchangeably with the word torque in the context of the rotating shaft 12 insofar as the force is being applied at a distance from the axis of rotation 20, which will result in a torque being applied to the shaft 12. As will be explained in more detail below, the rotation management system 32 includes a rotation initiator 34, an eddy current brake 36, and a latch 38. Also, as will be explained in more detail below, the rotation initiator 34 initiates the rotational movement of the remote shaft 12. 1679196 of 22 of the operating position, which is generally represented in Figs. 1, 3, and 5. The eddy current brake 36 controls the rotational speed of the shaft 12 as the shaft 12 approaches the stop position. The latch 38 resists the rotation of the shaft 12 away from the stop position. As can be understood from Figs. 1 to 4, the rotation mechanism 30 includes a weight 40 with a center of gravity 42 that is spaced from the rotation axis 20. The weight 40 is fixed to the shaft 12 and therefore moves with the shaft 12 between the operating and stopped positions. Since the center of gravity 42 is separated from the rotation axis 20, the weight 40 can be described as a counterweight that applies a torque to the shaft 12 by means of gravity, depending on the position of the center of gravity 42 with respect to the rotation axis 20. For example, when the center of gravity 42 is directly vertically above the rotation axis 20, as shown in Figs. 1 and 3, which is when shaft 12 is in the operating position, at most, weight 40 simply applies a force vertically downwards on shaft 12 without applying a torque to shaft 12.In such a condition, it can be said that the weight 40 is situated in a state of equilibrium about the axis of rotation 20. However, when the center of gravity 42 is located at a place other than directly vertical above the axis of rotation 20, the distance along the horizontal direction 26 between the axis of rotation 20 and the center of gravity 42 is the distance from the axis of rotation 20 at which the weight 40 is applied to the shaft 12 to result in a torque being applied to the shaft 12. 1679196 of 22 Thus, the rotation initiator 34 provides an initial rotation of the shaft 12 from the operating position shown in Figs. 1 and 3 to initiate the rotation of the shaft 12 from the operating position to the stopped position in case a stop is required when the stepper motor 24 is in an off condition. More specifically, and as can be understood from Figs. 3 and 4, the rotation initiator 34 includes a pair of permanent magnets, indicated in Figures 44A and 44B, which may be referred to collectively or individually in this document as 44. Each permanent magnet 44 includes a north pole 46 and a south pole 48 on opposite sides. The permanent magnet 44A is located on a strut 50 that is arranged on the support 14, and the permanent magnet 44B is located in a receptacle 52 that is formed on the weight 40.The permanent magnets 44 have their north and south poles 46 and 48 arranged so that they oppose each other when the shaft 12 is in the operating position of Fig. 3. In this respect, it can be said that weight 40 is in a first position when shaft 12 is in its operating position, as generally shown in Fig. 3, and it can also be said that weight 40 is in a second position when shaft 12 is in the stopped position, as generally shown in Fig. 4. In order to prevent the permanent magnets 44 from creating a condition in which the permanent magnets 44, with their mutual magnetic repulsion, are in a state of equilibrium, permanent magnets 44A and 44B are actually slightly offset from each other and not in a state of equilibrium when shaft 12 is in the operating position. The result is that the permanent magnets 44 apply another torque to shaft 12. 1679196 of 22 torque that pushes shaft 12 towards the stop position, but which is overcome by the stepper motor 24, while the stepper motor 24 is electrically energized. The displacement between the permanent magnets 44A and 44B is on the order of approximately 5 to 8 degrees of rotation of shaft 12, which means that the permanent magnets are positioned in such a way that they would directly oppose each other if shaft 12 were rotated 5 to 8 degrees, as the case may be, from the operating position. When shaft 12 is in its operating position and weight 40 is in its first position, as generally represented in Figs.1 and 3, the permanent magnets 44 are already offset from each other by approximately 5 to 8 degrees of rotation, so that a loss of electrical power in the stepper motor 24 will immediately result in the mutual opposition of the magnets rotating the shaft 12 beyond the initial rotation of 5 to 8 degrees of rotation towards the stop position. As can be understood from Figures 1 to 4, the center of gravity 42 of weight 40 is higher in the vertical direction 28 in the first position of Figures 1 and 3 than it is in its second position of Figures 2 and 4. Since the shaft 12 is oriented parallel to the horizontal direction 26, weight 40 in the first position has greater potential energy than in the second position, and this relatively greater potential energy is used to rotate the shaft 12 with the control drum 10 around it from the operating position to the stopped position. When weight 40 is in the second example position of Figures 2 and 4, the center of gravity 42 is located vertically below the axis of rotation. 1679196 of 22 20, which means that the center of gravity 42 in the second position and the center of gravity 22 are aligned with each other along the vertical direction 28. Therefore, it can be observed that the stepper motor 24, when energized, resists the opposing force of the permanent magnets 44 when the weight 40 is in the first position, and this holds the shaft 12 in the operating position. If the stepper motor 24 is turned off, however, the force provided by the permanent magnets 44 initiates the rotation of the shaft 12 to move the weight 40 from the first position to the second position. As soon as the center of gravity 42 shifts along the horizontal direction 26 from the axis of rotation 20, the gravity acting on the weight 40 causes the shaft 12 to continue rotating to the second position of weight 40, which is the stopping position of the shaft 12. Thus, gravity acting on the weight 40 causes the shaft 12 to rotate to the stopping position in the absence of electrical power applied to the stepper motor 24. However, it should be noted that the need for a stop can sometimes be urgent. In such a situation, it would be desirable to position shaft 12 in the stop position of Fig. 2 as quickly as possible. Such repositioning to the stop position would ideally be achieved without shaft 12 rotating beyond the stop position and oscillating back and forth through it until it finally settles into the stop position. Therefore, the eddy current brake 36 is provided to manage the rotational speed of shaft 12 as it approaches the stop position. 1679196 of 22 More specifically, the eddy current brake 36 includes a pair of permanent magnets designated as 54A and 54B, which may be referred to collectively or individually in this document as 54. Each permanent magnet 54 comprises a north pole 56 and a south pole 58, and the permanent magnets 54 are arranged on the support 14 such that one of the north poles 56 is oriented towards one of the south poles 58, so that the permanent magnets 54 attract each other. The eddy current brake 36 further includes a flywheel 60 located on and rotating with the shaft 12. The flywheel 60 is made of an electrically conductive material such as aluminum, copper, steel, or other suitable material.The flywheel 60 has a series of notches 62 formed on its interior to form several radially oriented fins 64 located between the notches and a solid portion 66 that is free of notches 62. According to the usage in this memory, the expression a number of and variations thereof shall refer broadly to any quantity other than zero, including a quantity of one. When weight 40 is in the first position of Fig. 3, some of the fins 64 are positioned between the permanent magnets 54, and the solid portion 66 is spaced vertically 28 above the space between the permanent magnets 54. As shaft 12 begins to rotate from the operating position of Fig. 3 to the stopped position of Fig. 4, a subset of the fins 64 successively moves across the space between the permanent magnets 54. When the solid portion 66 begins to move between the permanent magnets 54, the currents of 1679196 of 22 Eddy currents are induced in the solid portion 66 by the magnetic field of the permanent magnets 54, where it is reiterated that the south and north poles 56 and 58 are arranged in such a way that they attract each other. According to Lenz's Law, the eddy currents induced in the solid portion 66 will create their own magnetic fields that oppose the field of the permanent magnets 54, where such magnetic opposition reduces the rotational speed of the shaft 12. The aforementioned eddy currents are not induced to a significant extent in the fins 64, since they are relatively small along the circumferential direction compared to the solid portion 66. The braking of shaft 12 by the rotating solid portion 66 being held between the permanent magnets 54 has the effect of slowing the rotation of shaft 12, allowing it to be positioned so that the center of gravity 42 of the weight 40 is in its lowest possible vertical position. In other words, the braking force applied to the solid portion 66 by the eddy current brake 36 depends directly on the rotational speed of shaft 12 and the solid portion 66 attached to it.As the rotational speed of shaft 12 slows, the magnetic braking force decreases accordingly, and weight 40 is allowed to move to a position where the center of gravity 42 is located vertically below the axis of rotation 20 without weight 40 moving beyond that position and then oscillating back and forth about that position until weight 40 naturally reaches its lowest point. Conversely, since the permanent magnets 54 retard the solid portion 66 by applying a force of 1679196 of 22 magnetic braking, which is based on the speed of the solid portion 66, the movement of the solid portion 66 is essentially slowed to the point where the effect of gravity on the weight 40 keeps it such that the center of gravity 42 is in its lowest possible position without having moved beyond its lowest possible position. This quickly moves the shaft 12 from its operating position to its stopped position without any back-and-forth oscillation around the stopped position. This results in a rapid stop of the nuclear environment 8, which is desirable. As previously stated, the rotation management system 32 also includes the bolt 38, which is generally represented in Figs. 1, 2, 5, and 6. The bolt 38 includes a pin 68, which can be said to constitute a first portion of the bolt 38, and also includes a receptacle 70 formed on the shaft 12, which can be said to constitute a second portion of the bolt 38. The bolt 38 also includes an actuator 72, which is in the form of a linear actuator and is located on the support 14. The linear actuator can be operated to move the pin 68 between a first location, as generally represented in Fig. 6, which corresponds to a locked position of the bolt 38, and a second location, as generally represented in Fig. 5, which corresponds to an unlocked position of the bolt 38. Actuator 72 is electrically energized, but pin 68 does not move between the first and second locations unless actuator 72 is energized. Therefore, when it is desired to place shaft 12 in a stop configuration, shaft 12 is rotated to its stop position, and actuator 72 is energized to linearly move pin 68 from the 1679196 of 22 second location of Fig. 5 to the first location of Fig. 6, in which position the pin 68 is received in the receptacle 70. The pin 68 that is received in the receptacle 70 resists the movement of the shaft 12 out of the stop position. The pin 68 is held in the first position, regardless of whether the actuator 72 is electrically energized or not. Thus, the shaft 12 can remain in a stop configuration during the transport of the nuclear environment 8, for example, whether the actuator 72 is electrically energized or not. When it is desired that the shaft be unlocked, actuator 72 is energized to return pin 68 from the first position in Fig. 6 to the second position in Fig. 5, and stepper motor 24 can be energized to rotate shaft 12 from the stop position in Fig. 6 to the operating position in Fig. 5. Therefore, it can be understood that the rotating device 4 can cause the control drum of the device 6 to rotate from the operating position to the stopped position in the event of a loss of electrical power to the stepper motor 24. Furthermore, the latch 38 retains the shaft 12 in the locked position of Fig. 6, regardless of whether the actuator 72 remains electrically energized after the bolts 68 have been moved to the first location shown in Fig. 6. This combination of features advantageously allows the nuclear environment 8 to be stopped quickly as required, even in the event of a power failure to the stepper motor 24, and the nuclear environment 8 is held in the stopped position by the latch 38, regardless of whether electrical power is available to the actuator 72. Other benefits will become apparent. 1679196 of 22 An improved control drum apparatus 106 is depicted in Fig. 7 and is partially depicted in Figs. 8 to 11. The control drum apparatus 106 includes an improved rotating apparatus 104 according to a second embodiment of the disclosed and claimed concept. The control drum apparatus 106 is similar to the control drum apparatus 6 in that it includes a control drum 110 located on a shaft 112 that is rotatably arranged in the support 114, wherein the control drum 110 includes a reflective portion 116 and an absorbing portion 118, and wherein the shaft 112 can be rotated about a rotation axis 120 by means of the operation of a stepper motor 124. The rotation apparatus 104 is different from the rotation apparatus 4 because it includes a rotation mechanism 130 and a rotation management system 132 that are different from the rotation mechanism 30 and the rotation management system 32. More specifically, the rotation mechanism 130 includes a spring 133 that extends between the support 114 and the shaft 112 and which, in the operating position of Fig. 8, is elastically deflected such that the spring 133 pushes the shaft 112 from the operating position of Fig. 8 to the stopped position of Fig. 9. The stepper motor 124 resists this push when it is energized. The spring 133 thus applies to the shaft 112 the force, i.e., the torque, required to rotate the shaft 112 from the operating position of Fig. 8 to the stopped position of Fig. 9 when the stepper motor 124 is de-energized. In this way, the spring 133 also serves as a rotation initiator 134 for the rotation management system 132. The rotating apparatus 104 additionally includes a current brake of 1679196 of 22 Foucault 136 which can cooperate with a flywheel 160 in order to slow the rotational speed of the shaft 112 when a solid portion 166 of the flywheel 160 is being received between a pair of permanent magnets 154 of the eddy current brake 136, which is when the shaft 112 begins to come to a stop position. In the exemplary embodiment shown, the spring 133 is elastically in a free and undeflected state in the stop position of Fig. 9. The operation of the eddy current brake 136 on the flywheel 160 reduces the rotational speed of the shaft 112 as the shaft 112 begins to approach the stop position, so that the shaft 112 comes to rest in the stop position where the spring 133 is elastically in a free and undeflected state. This advantageously prevents the shaft 112 from moving beyond the stop position of Fig. 9 and oscillating back and forth in opposite directions with respect to the stop position, which advantageously brings the shaft 112 to a stop quickly and allows for the shutdown of a nuclear environment 108 in which the control drum apparatus 106 is located. However, it is understood that, in alternative embodiments, the rotation mechanism 130 or the rotation management system 132, or both, may include, for example, a radially projecting structure located on the shaft 112 and a fixed stop located on a support 114. With such a geometry, the spring 133 can be configured to remain in an elastically deformed position even when the shaft 112 is in the stopped position and would therefore push the radially projecting structure against the fixed stop in order to retain the shaft 112 in the 1679196 of 22, stop position of Fig. 9. In this respect, it is understood that the use of such a spring in combination with a radially projecting structure and a fixed stop could potentially eliminate the eddy current brake 136. Such a scenario is entirely feasible. However, it is understood that the rotational speed of the shaft 112 when it reaches the stop position may be unknown, and the coupling of the radially projecting structure with the fixed stop could result in a certain level of rotational oscillation of the shaft 112 if the radially projecting structure were to bounce off the fixed stop. Thus, the eddy current brake 136 could still be usefully provided in combination with such a radially projecting structure and a fixed stop. The rotation management system 132 further includes a latch 138 comprising an actuator 172, a bolt 168, and a receptacle 170. More specifically, the actuator is in the form of a linear stepper motor 176 located on a first bracket 172 of the support 114, a swivel seat 180 located on a second bracket 178 of the support 114, and a threaded shaft 182 extending between the stepper motor 176 and the swivel seat 180. The threaded shaft includes a threaded collar 184 threaded onto it and to which the bolt 168 is attached. When the stepper motor 176 is electrically energized, it rotates the threaded shaft 182, which causes the threaded collar 184 to move non-rotationally along the threaded shaft 182 between the first and second brackets 174 and 178, while carrying the bolt 168 with it. That is, when the threaded shaft 182 rotates, the threaded collar 184 does not rotate with it; rather, the threaded collar 184 moves non-rotationally. 1679196 of 22 along the threaded shaft 182. As such, the actuator 172 is electrically operated to move the bolt 168 between a first location, as usually depicted in Fig. 11, which is a locking position of the bolt 138, and a second location, as usually depicted in Fig. 10, in which the bolt 138 is in an unlocked position. When the bolt 138 is in the locked position, the pin 168 is received in the receptacle 170, in which the pin 168 resists the rotation of the shaft 112 away from the stop position of Fig. 11. When the bolt 138 is in the unlocked position, the pin 168 is separated from the receptacle 170, which allows the shaft 112 to rotate between the stop position of Fig. 11 and the operating position of Fig. 10. Since actuator 172 ceases movement if it is not electrically energized, it can remain unenergized in the locked position of the latch 138, such as during transport of the nuclear environment 108 containing the control drum 106. Simultaneously, it keeps shaft 112 in the stopped position regardless of whether electrical power is supplied to actuator 172. This advantageously keeps shaft 112 in the stopped position and thus prevents unintentional startup of the nuclear environment 108. Furthermore, the rotation mechanism 130 and the rotation management system 132 rotate shaft 112 from the operating position to the stopped position very quickly when the stepper motor 124 becomes electrically unenergized. This enables a rapid shutdown of the nuclear environment 108 containing the control drum 106. It is understood that any of the teachings contained herein The teachings 1679196 of 22, concerning rotary apparatus 104, may be implemented in rotary apparatus 4, without departing from the spirit of this disclosure. In this respect, any of the teachings may be combined in any manner to produce advantageous rotary apparatuses that are within the scope of this disclosure. Other variations will be evident. Although specific embodiments of the invention have been described in detail, those skilled in the art will appreciate that various modifications and alternatives to those details could be developed in light of the general lessons of the disclosure. Accordingly, the particular embodiments disclosed are intended only to be illustrative and not limiting as to the scope of the invention, which will be given the full extent of the appended claims and any and all equivalents thereof.

Claims

1. A rotation system that can be used with a control drum in a nuclear environment, characterized in that it comprises: a motor; a control drum comprising a shaft, wherein the shaft comprises a reflective portion and an absorbing portion, wherein the shaft is configurable between an operating configuration, wherein the reflective portion is oriented towards a core of a nuclear environment, and a stop configuration, wherein the absorbing portion is oriented towards the core, wherein the shaft is operatively coupled to the motor, wherein the shaft is configured to transition to the operating configuration upon the motor being energized, and wherein the shaft is configured to transition to the stop configuration upon the motor being de-energized;and an eddy current brake configured to control the rotational speed of the shaft as the shaft approaches the stop configuration, wherein the eddy current brake comprises: a first magnet; a second magnet, wherein the first magnet and the second magnet are fixed relative to each other; and a rotatable conducting disk between the first magnet and the second magnet, wherein the conducting disk comprises: a plurality of radially oriented fins, each fin comprising a first arc length; and a solid portion comprising a second arc length greater than the first arc length. 17 Claims follow;